Central heating system - advice required

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We've just inherited a central heating system in a recently purchased house.
The boiler is a Baxi Solo 18HE and appeared to be a fairly standard setup with 2 header and expansion tanks in the loft and a hot cylinder......

The timer and thermostat controls seem a bit old though (Randall 103e) and Randall TP5.

There is no mention of hot water anywhere on the timer so I reckon it is a single channel device. The thermostat appears to open and close a single 2 port motorised valve. There is an old looking thermostat strapped to the cylinder.

The layout of the pipes from the boiler is like this

BOILER

PUMP--------------VALVE---------------Radiators (flow)
|
------------------------------CYLINDER (flow)

What seems to happen is that with the room CH thermostat set to off the hot water heats up in the cylinder and then is shut down by the cylinder stat. (which turns the boiler off)

But with the room stat set to on then it will heat both CH and HW.....(but what controls the temperature of the HW)

Do I need to have another valve put in attached to a cylinder thermostat?

It seems a bit limited to me

Any advice gratefully accepted
 
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it sounds like a Gravity HW system. It can be converted by adding another motorised valve, which will prevent heat going to the cylinder just because the heating is on, but it will be more efficient to make it fully pumped. This will heat the cylinder faster. If you insulate the HW circulation pipes as well as adding the valve and making it pumped, you will save more money on gas.

BTW as it is quite old, it is worth giving it a clean with Sentinel X400 for 4 weeks or so before having it drained for the work (you may as well wait until the heating season is over). there will be a lot of old sediment in the system, especially in the gravity pipes as they have so little flow. If you can afford an extra £100 and see signs of a sediment problem, it is worth having a Magnaclean added on the return to the boiler, I guarantee you will be amazed and delighted to see how much black sludge it traps. It will be very little extra work to fit it while the other changes are being made.

You can take the opportunity to update the programmer and thermostats while you are at it, some of the new programmable thermostats are very sophisticated (unless like me you are too set in your ways to learn how to work them, or have an elderly person in the house).
 
There is no mention of hot water anywhere on the timer so I reckon it is a single channel device.
Do I need to have another valve put in attached to a cylinder thermostat?

It seems a bit limited to me

Any advice gratefully accepted
yes it would be better,you would need to upgrade the programmer and wiring too
 
If as has been suggested that a solo 18he may be on gravity then you have a real problem.I have never seen a 18HE fitted on gravity!! A little more accurate system details will help. No doubt you have a fully pumped system that requires controls to be added/updated.18HE boilers will not work on gravity.
 
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if I'm understanding his drawing correctly it's fully pumped,it tees of after the pump and feeds the cylinder directly and the rads via the zone valve

Matt
 
If as has been suggested that a solo 18he may be on gravity then you have a real problem.I have never seen a 18HE fitted on gravity!! A little more accurate system details will help. No doubt you have a fully pumped system that requires controls to be added/updated.18HE boilers will not work on gravity.

Thanks for all the replies....how do I find out if it is a gravity system?

It would appear that the CH is pumped and the HW is gravity fed but the pump must be pushing some water to the cylinder...

Here is a link to a rough diagram.....Cheers

http://www.websters-furniture.co.uk/Assets/Images/CH-HW_diag.jpg[/img]
 
if I'm understanding his drawing correctly it's fully pumped,it tees of after the pump and feeds the cylinder directly and the rads via the zone valve

Matt

Yes, you're quite right. It tees off after the pump with the zone valve on the CH branch and then nothing on the HW branch (just straight to the cylinder and back)
 
Yes, you're quite right. It tees off after the pump with the zone valve on the CH branch and then nothing on the HW branch (just straight to the cylinder and back)
Then all you need is a second valve in the pipe from the T junction to the cylinder. This arrangement is called an S PLan. You can then uses a two channel programmer to have separate CH and HW times/temperatures.

View media item 71 View media item 72
 

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